Your best bet is looking through the classifieds here and trying to look for the figures you need.
Everyone lists the prices of their figures on their posts.
You can also post your WANTS list and have people who may have those figures contact you via PM (Private Message).
For example, your post could read (in the subject line) "Need: Commanders Gree/Cody, etc."
Then in your post list all the figures you want to buy. If you're new here, make sure you read the
Classified Regulations to see how this all works.
From here people who have those figures may contact you with their prices and/or links to their posts of figures they are selling that you may need.
Good luck.